Map NetCDF API Syntax to MATLAB Syntax - MATLAB & Simulink (original) (raw)
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MATLAB® provides access to the functions in the netCDF C library through a set of low-level functions that are grouped into a namespace callednetcdf. Use the functions in this namespace to read and write data to and from netCDF files. To use the MATLAB netCDF functions effectively, you should be familiar with the netCDF C interface.
Usually, the MATLAB functions in the netcdf namespace correspond directly to routines in the netCDF C library. For example, the MATLAB function netcdf.open corresponds to the netCDF library function nc_open. In some cases, one MATLAB function corresponds to a group of netCDF library functions. For example, instead of creating MATLAB versions of every netCDF librarync_put_att_ _`type`_ function, where_type_ represents a data type, MATLAB uses one function, netcdf.putAtt, to handle all supported data types.
To call one of the functions in the netcdf namespace, you must prefix the function name with the namespace. The syntax of the MATLAB functions is similar to that of the netCDF library functions. However, the netCDF C library functions use input parameters to return data, while their MATLAB counterparts use one or more return values. For example, this is the function signature of the nc_open function in the netCDF library:
int nc_open (const char *path, int omode, int ncidp); / C syntax */
The netCDF file identifier is returned in the ncidp argument.
This is the signature of the corresponding MATLAB function, netcdf.open:
ncid = netcdf.open(filename,mode)
Like its netCDF C library counterpart, the MATLAB netCDF function accepts a file name and a constant that specifies the access mode. However, the MATLABnetcdf.open function returns the file identifier,ncid, as a return value.
The MATLAB netCDF functions automatically choose the MATLAB class that best matches the netCDF data type. This table shows the default mapping.
| NetCDF Data Type | MATLAB Class |
|---|---|
| NC_DOUBLE | double |
| NC_FLOAT | single |
| NC_INT64 (NetCDF-4 files only) | int64 |
| NC_UINT64 (NetCDF-4 files only) | uint64 |
| NC_INT | int32 |
| NC_UINT (NetCDF-4 files only) | uint32 |
| NC_SHORT | int16 |
| NC_USHORT (NetCDF-4 files only) | uint16 |
| NC_BYTE | int8 |
| NC_UBYTE (NetCDF-4 files only) | uint8 |
| NC_CHAR | char |
| NC_STRING (NetCDF-4 files only) | string |
| User-defined NC_VLEN types (NetCDF-4 files only) | cell |
You can override the default and specify the class of the return data by using an optional argument to the netcdf.getVar function.